1. Field of the Invention
The present invention relates to systems for moving material from one location to another, and more particularly, to such systems used for moving scrap metal from a scrap metal bin to an electric arc furnace.
2. Description of the Prior Art
In typical manufacturing plants, such as in steel foundries, scrap metal is brought into the plant by rail or by truck, and the scrap metal is then typically placed in a storage device such as a storage bin. A schematic plan view of a part of a representative steel foundry is illustrated in FIG. 1, where a set of rail tracks is designated 10, and scrap metal bins are shown at 12-16. Downstream of the scrap metal bins 12-16 are located one or more furnaces, commonly electric arc furnaces, designated 20-24 in FIG. 1.
To move material from the bins 12-16 to the furnaces 20-24, systems for moving material from one location to another have been used. In the illustrated foundry, the material to be moved is scrap metal.
A representative material-moving system is illustrated in FIGS. 1-2, and is generally designated 26. The material-moving system 26 includes an overhead gantry 28 comprising a pair of spaced rails 30. A two-piece bridge 32 spans the rails 30, and includes wheels 34 at the ends of each piece of the bridge. The wheels travel along the rails 30 so that the bridge 32 may be moved along the gantry 28 in opposite directions. The two pieces of the bridge 32 are connected by a trolley 36. The trolley 36 is movable along the bridge 32 in opposite directions. The motion of the bridge 32 and the motion of the trolley 36 are both substantially horizontal. The motion of the trolley 36 on the bridge 32 is substantially at right angles to the motion of the bridge 32 on the gantry 28. Thus, the trolley 36 may be moved in both the X and Y directions through controlled movement of the bridge 32 and trolley 36.
The material-moving system 26 includes a container 37 for material to be moved, a vertically-movable main hook 38 and a vertically-movable auxiliary hook 40. The movements of the hooks 38, 40, bridge 32 and trolley 36 are controlled by an operator in a cab, typically positioned along the bridge 32, as shown at 39 in FIGS. 1-2. Thus, the operator is generally positioned above the factory floor 41. Both hooks 38, 40 are suspended from the trolley 36. Thus, the hooks 38, 40 move in unison with the trolley 36 in the X and Y directions, and move independently in the Z or vertical direction.
As shown in FIGS. 3-4, the container 37 for material to be moved has a hollow main body 42 with an exterior surface 44, an open interior 46 and top and bottom openings 48, 50 leading into the open interior 46 of the main body 42. There is at least one movable structure 54, 56 for covering and uncovering one of the openings 50 into the open interior 46 of the main body 42. There is at least one actuator 58, 60 connected to each movable structure 54, 56.
As shown in FIGS. 3-4, a two-piece saddle 62 extends outwardly from the exterior surface 44 of the main body 42 of the container 37. A target member or ring 64 is supported on the saddle 62 and connected to the actuator 58, 60 so that the opening 50 to the container 37 can be uncovered by pulling on the target member 64.
In the illustrated steel foundry, the container 37 comprises a scrap charge bucket for scrap metal. There are two movable structures 54, 56 for covering and uncovering the bottom opening 50 into the open interior 46 of the main body 42; these two movable structures 54, 56 are pivotable, and open in a general clam shell manner, as shown in FIG. 4. There are two actuator cables 58, 60: one actuator cable 58, 60 is attached to each pivotable clam shell structure 54, 56, and both actuator cables 58, 60 are attached to the target member 64. The target member 64 defines a ring that is supported on the saddle 62.
The saddle 62 comprises two saddle plates 66, 68 fixed to the exterior surface 44 of the scrap charge bucket main body 42. One saddle plate 68 is shown in FIG. 4A; each saddle plate 68 has a support surface 70 and an upstanding retention member 72 that meet in a nook 74. The target ring 64 straddles the two saddle plates 66, 68, and rests on the support surfaces 70 in the nooks 74. To open the pivotable clam shell structures 54, 56, the target ring 64 is lifted off the saddle 62 and pulled upwards, as shown in FIG. 4.
To carry the scrap charge bucket 37 and to open the pivotable clam shell structures 54, 56, the main and auxiliary hooks 38, 40 are used. Both the main and auxiliary hooks 38, 40 are suspended from the trolley 36, and both hooks 38, 40 are movable substantially vertically on the trolley 36. In one production stage in a steel foundry, the main hook 38 is used to pick up the empty scrap charge bucket 37, to move the empty scrap charge bucket near to the scrap bins 12-16 for filling with scrap metal, and to move the filled scrap charge bucket to one of the furnaces 20-24 for unloading the scrap metal into the furnace. At another stage of production, the main hook 38 is used to move an empty ladle to one of the electric arc furnaces for filling with molten metal, and to move the filled ladle. Depending on the type of production employed at the plant, the ladle may be moved to molds so that the molds may be filled with molten metal, or the ladle may be moved to another area of the plant for use in bottom pressure casting, for example.
In plants having only two hooks, the auxiliary hook 40 is used for different purposes at different times of production. Commonly, the auxiliary hook 40 is used to capture and lift the target ring 64 off of the saddle on the scrap charge bucket, pulling the target ring 64 until the pivotable clam shell bottom members 54, 56 are opened so that the scrap metal may be dropped into the furnace. The auxiliary hook 40 is also used to replace the target ring 64 on the saddle 62 of the scrap charge bucket 37. At other stages of production, the auxiliary hook 40 is used to lift and move a large electromagnet 76, shown at in FIG. 3, to move scrap metal from the rail car or scrap bins 12-16 or to load the scrap charge bucket 37 with scrap metal. This electromagnet 76 is sometimes also used inside the electric arc furnace 20-24 to remove excess scrap metal, to unload additional scrap into the furnace, or to level the scrap metal in the furnace. The auxiliary hook 40 may be used to carry tools other than a magnet, such as other general and special tools supplied by overhead crane suppliers, for example.
In plants with only one auxiliary hook 40, the performance of its various functions has required that the auxiliary hook 40 sometimes carry the magnet 76 and sometimes operate without the magnet 76. This leads to downtime as the magnet 76 is removed and replaced. In some other typical plants, three hooks are provided so that the magnet can remain on one of the hooks while the third hook is used to operate the mechanism that opens the scrap charge bucket 37. This solution saves time but adds to the cost and complexity of the systems at the plant.
In any event, use of the hooks requires some skill and visual acuity on the part of the crane operator, who must be able to see the target ring 64, for example, and be able to manipulate the hooks into their proper positions from the operator's position in the cab 39, typically at some distance from the hook.